Rare earth magnet and method therefor

a rare earth magnet and magnet technology, applied in the field can solve the problems of difficult application of magnets to motors with medium to high output, and significant lowering of etc., to achieve the effect of increasing the electric resistance significantly lowering the magnetic characteristics of rare earth magnets, and medium to high outpu

Inactive Publication Date: 2005-06-23
NISSAN MOTOR CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0006] As shown in JP-A-10-321427, SiO2 and / or Al2O3 present at the boundary of magnetic particles for rare earth magnet can increase electric resistance of the rare earth magnet. However, when SiO2 and / or Al2O3 are added alone to the rare earth magnet, magnetic characteristics thereof are significantly lowered, making application of the magnet to a motor with medium to high output difficult.
[0009] It is an object of the present invention to provide a rare earth magnet that can effectively suppress eddy current and has less degradation of magnetic characteristics by suppression means of eddy current. It is also an object of the present invention to provide a method for stable production of such a rare earth magnet.

Problems solved by technology

However, when SiO2 and / or Al2O3 are added alone to the rare earth magnet, magnetic characteristics thereof are significantly lowered, making application of the magnet to a motor with medium to high output difficult.
A metal oxide (MO(n / 2)) of a metal M (Si, Zr, Ti, Al, Cr, Ce and Co) described in JP-A-6-69009 is so poor in thermodynamic stability that chemical reaction proceeds between magnet particles and a metal oxide layer (MO(n / 2)) in a fixing step by heating under compression, resulting in significantly lowered magnetic characteristics of the rare earth magnet.
Consequently, when an amorphous metal oxide layer (MO(n / 2)) is formed at the boundary of magnet particles by a sol-gel method starting from a metal alkoxide of a rare earth element including Y, produced sol is easily gelled, then posing a problem of forming a coated film with rough surface caused by gel particles grown large in a liquid or a problem of forming turbid liquid or deposit caused by gelation of most part of sol.
In other words, stable production of a rare earth magnet is difficult, when sol containing an alkoxide of a rare earth element such as Y is used for producing a rare earth magnet.
As described above, conventional technologies have posed problems of significantly lowering of magnetic characteristics and inability of stable production of a rare earth magnet, although they can suppress eddy current generation by increasing electric resistance of a rare earth-magnet.

Method used

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  • Rare earth magnet and method therefor
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  • Rare earth magnet and method therefor

Examples

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example 1

[0060] As magnet powder for rare earth magnet, Nd—Fe—B type anisotropic magnet powder, prepared by using a known HDDR method, were used. The procedure for producing the magnet powder for rare earth magnet is as follows. First, an ingot with composition of Nd12.6FebalCo17.4B6.5Ga0.3Al0.5Zr0.1 was prepared. This ingot was homogenized by holding at 1120° C. for 20 hours. The homogenized ingot was hold in hydrogen atmosphere while increasing the temperature from room temperature to 500° C., then up to 850° C., followed by holding under vacuum atmosphere at 850° C. and cooling to obtain an alloy having recombined cluster texture (crystal grains) showing a fine ferromagnetic phase. This alloy was pulverized under argon gas atmosphere by use of a jaw crasher and a brown mill to obtain magnet powder for rare earth magnet having the average particle diameter of not larger than 425 μm.

[0061] Tb4O7 powder as terbium oxides and the magnet powder for rare earth magnet were mixed to obtain a mix...

example 2

[0065] As magnet powder for rare earth magnet, Nd—Fe—B type anisotropic magnet powder, produced by using a known HDDR method in similar way to Example 1, were used. As a method for producing the rare earth magnet, the following method was adopted; terbium triisopropoxide, which is terbium alkoxide, was coated on the surface of the magnet powder for rare earth magnet, polycondensating the resultant by hydrolysis and heat treatment of terbium triisopropoxide, and thus obtained magnet powder for rare earth magnet were used, at the surface of which terbium oxide is bound. Detailed procedure is as follows:

[0066] (1) 200 g of terbium triisopropoxide as terbium alkoxide was dissolved by adding dewatered hexane as an organic solvent in a glove box filled with argon gas, where the dew point is not higher than −80° C., and then liquid for terbium surface treatment was prepared in the total volume of 1000 ml.

[0067] (2) 180 mL of the liquid for terbium surface treatment was added into 1000 g ...

example 3

[0073] As magnet powder for rare earth magnet, Nd—Fe—B type anisotropic magnet powder, produced by using a known HDDR method in similar way to Example 1, were used. As a method for producing the rare earth magnet, the following method was adopted; terbium triisopropoxide, which is terbium alkoxide, was coated on the surface of the magnet powder for rare earth magnet, polycondensating the resultant by hydrolysis and heat treatment of terbium triisopropoxide, and thus obtained magnet powder for rare earth magnet were used, at the surface of which terbium oxide is bound. Detailed procedure is as follows:

[0074] (1) 150 g of terbium triisopropoxide as the terbium alkoxide was dissolved by adding dewatered tetrahydrofuran as an organic solvent in a glove box filled with argon gas, where the dew point is not higher than −80° C., and then liquid for terbium surface treatment was prepared in the total volume of 1000 ml.

[0075] (2) 360 mL of the liquid for terbium surface treatment was added...

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Abstract

A rare earth magnet includes rare earth magnet particles; and amorphous and / or crystalline terbium oxide present at the boundary of the rare earth magnet particles and represented by the formula: TbOn, wherein 1.5<n≦2. The rare earth magnet prevents decrease eddy current effectively.

Description

Background of the Invention [0001] 1. Field of the Invention [0002] The present invention relates to a rare earth magnet having high electric resistance, and in particular, relates to a rare earth magnet with high electric resistance to be used in a motor for electronic equipment and automobile driving. [0003] 2. Description of Related Art [0004] An inexpensive ferritemagnet has conventionally been used widely as a magnet for a permanent magnet type motor. However, use of a rare earth magnet with higher performance has been increasing year by year with demand for development of more compact rotating electrical appliances with higher performance. Development of a rare earth magnet, represented by Sm—Co type magnet and Nd—Fe—B type magnet, is under way, aiming at higher performance and lower price. A rare earth magnet, however, has low electric resistance because it is a metal magnet, leading to a problem of lowering a motor efficiency due to increased eddy-current loss when built in ...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B22F1/02B22F3/02C22C33/02H01F1/057H01F1/08H01F1/09H01F41/02H02K1/02H02K1/27
CPCH01F1/0576H02K1/278H02K1/02H01F1/08H02K1/2781
Inventor TAYU, TETSUROUONO, HIDEAKIONO, TAKAEKAWASHITA, YOSHIOKANO, MAKOTOSHIMADA, MUNEKATSU
Owner NISSAN MOTOR CO LTD
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